At least 99 American soldiers killed themselves last year, the US army's highest suicide rate in 26 years, according to a new report.

The rate of 17.3 suicides per 100,000 soldiers compares with 12.8 in 2005, officials said.

Twenty-eight of the soldiers who took their own life last year did so while serving in Iraq or Afghanistan.

The army listed failed relationships, legal and financial issues and work stress as factors behind the suicides.

Two soldiers' deaths from last year are still being investigated. If confirmed as suicide, the figure for 2006 will climb to 101.

The highest number recorded was 102 in 1991, the year of the Gulf War - but more soldiers were on active duty then, meaning the rate per 100,000 soldiers was lower than in 2006.

So far this year, 44 soldiers have taken their own lives, 17 of them while deployed to Iraq or Afghanistan.

Mental health care

The report said there was "limited evidence" to support the suspicion that repeated deployments to Iraq and Afghanistan were putting more servicemen and women at risk of suicide.

Its authors found a significant relationship between suicide attempts and the length of time soldiers spent in Iraq, Afghanistan or in nearby countries in operations supporting those wars.

A study published in March this year found a quarter of US veterans treated at veterans' health centres after returning from Iraq and Afghanistan suffered mental health problems.

The most frequent diagnosis was post-traumatic stress disorder, but anxiety, depression and substance-use also counted as mental health problems.

Other studies have found that the US military's mental health care resources have not been adequate for the large numbers of servicemen and women needing help as the wars in Iraq and Afghanistan continue.

The US army has revised training programmes and is doing more to prevent suicides, the Associated Press news agency says.

It has also recruited more psychiatrists and other mental health professionals and is encouraging soldiers to recognise their own problems and seek help without fear of stigma.